Generally, 3D printing involves the use of an inkjet type printhead to deliver a liquid or colloidal binder material to layers of a powdered build material. The printing technique involves applying a layer of a powdered build material to a surface typically using a roller. After the build material is applied to the surface, the printhead delivers the liquid binder to predetermined areas of the layer of material. The binder infiltrates the material and reacts with the powder, causing the layer to solidify in the printed areas by, for example, activating an adhesive in the powder. The binder also penetrates into the underlying layers, producing interlayer bonding. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final object is formed. See, for example, U.S. Pat. Nos. 6,375,874 and 6,416,850, the disclosures of which are incorporated herein by reference in their entireties.
Apparatus for carrying out 3D printing typically move the printheads over the print surface in raster fashion along orthogonal X and Y axes. In addition to the time spent printing, each printhead move requires time for acceleration, deceleration, and returning the printhead to the starting position of the next move. The inefficiencies inherent in these reciprocating motions reduce the productivity of the 3D printing process.
It is, therefore, an object of the present invention to provide apparatus and methods for continuously and efficiently performing 3D printing.